Bird Migration

Migration: Bird Migration Seasonal movement from one habitat to another to take advantage of resource (food) surpluses. Often happens because winter range cannot supply enough of the right types of food to raise offspring.

To migrate or not to migrate? That is the question! Many birds do not need to migrate because they are able to switch between seasonably available foods.

Where shall we go? Bird migration usually happens in a north-south direction following the warm season. In mountainous regions, migration may happen vertically (high elevation in summer, low in winter). Migration can also be east-west, as in the case of certain gulls and loons.

                                                                                                                                                                                                                Frequent Flyer Miles Depending on species, migration may be anywhere from a few miles up and down a mountain slope to the arctic tern’s 20,000-mile round trip from Arctic to Antarctic.

Anybody got a compass? Navigation strategies: Internal clock Sun position Star position Topographic landmarks Infrasound Air pressure Magnetic field Most first-year offspring DO NOT learn route by following adults. (Exception – waterfowl & cranes)

Hazard Ahead! Towers & skyscrapers Light pollution Exposure to predators (esp. cats) Storms blow migrants out to sea Habitat destruction may eliminate critical refueling/rest stops.

                     

Migration patterns of many birds have coevolved with the occurance of critical food resources along the route.

A ruby-throated hummingbird weighs 3 grams, or one tenth the weight of a first-class letter. Ruby-throated hummingbirds fly up to 500 miles non-stop across the Gulf of Mexico on their migration. Before starting, they increase their body weight by 50%, storing energy as fat to burn while crossing. More migration